The unique and valuable role of radioactive tracer materials in a variety of testing and research problems has been clearly established. The use of such tracers, however, can only be fully realized if highly sensitive techniques are available for detecting their presence. Two important pieces of information are sought in tracer experiments; (a) the amount of isotope present and (b) its location. The techniques for determining the location of tracers—termed autoradiography—is discussed in this paper.